Programmable MSD 6AL-2 questions

[SSLance]

So, a year later I am revisiting this topic. It was interesting to read back and see what I bailed on last year and attempting again this year with the new engine.

Last year I disconnected the MAP sensor and just ran the run retard graph in the box and it did pretty good all year. With the new engine, and new train of thought...I'm trying to program in a "boost retard" curve once again.

My engine builder concentrates on race engines and we dynoed this engine at 32* locked out 0-6500 RPM. I initially started with the run retard curve in the MSD that I ran last year that pulled 10* out at idle ramping up to all in at 2000 RPM. (22* at idle, 32* 2000+RPM) It ran pretty well but the idle was a bit unstable, most wouldn't have noticed it but while trying to tune the carb it was kind of giving me fits. I finally took the builder's advice and locked in 32* 0-6000 RPM. That cleaned the idle up a lot and I was able to get the carb dialed in nicely. It pulls about 17" of vacuum idling at 850 RPM with an AFR of 14, cruise AFRs are right around 15 and it gets a bit fat under WOT around 12-13 depending on what RPM I start the pull at. It runs very smooth, makes great power, and is safe if I get a bad tank of gas somewhere.

The only issue is it will ping if I lug it down under 2000 RPM in 3rd, 4th or 5th gear. I have to try to make it ping, under normal driving circumstances I can not hear any detonation.

So I have put the MAP sensor back in place and am working on using the Boost Retard function to try to pull some timing out under low vacuum situations.

Here are the dials at idle completely warmed up.



It idles around 5.25 PSI, will drop to 3.5 PSI under full engine compression like downshifting coming to a stop and the highest I've seen is about 13.75 PSI at WOT in 3 or 4th gear. I created this Boost Retard graph and drove it.



It's basically pulling 10* of timing out (32-10=22*) when vacuum drops under WOT pulls and stopped the pinging. The thing is, at WOT the PSI gains to 13.75 and the box stay at 5* retard (27*)...never letting the timing get back up to the 32*s it needs.

I'm thinking about pulling the right dot that is right now at 14.5 to the left and putting it at about 13, that way at just less than WOT the box would put the full timing amount back in, only retarding the timing between 10-13 PSI.

Am I thinking correctly here? I can't seem to find a way to pull timing out at WOT (zero vacuum) at low RPMS, but not pull the same timing out at WOT at higher RPMs where the timing is needed. So my hard head is thinking to just tell the box to pull the timing at just about WOT...